LOGGER :: info不作为s使用-> LOGGER.info

Question

I have defined a logger instance as follows:

private static final Logger LOGGER = Logger.getLogger(Main.class.getName());

I have an array of strings that I want to log, so I used the following:

Arrays.stream(new String[]{"ABC", "DEF", "XYZ"}).forEach(LOGGER::info);

However, nothing is printed into the log. But, if I change the reference method to an equivalent lambda form, it prints into the log:

Arrays.stream(new String[]{"ABC", "DEF", "XYZ"}).forEach(s -> LOGGER.info(s));

What am I missing here?

I tried the following approaches as well and they all behave the same:

Stream.of("ABC", "DEF", "XYZ").forEach(LOGGER::info);
List.of("ABC", "DEF", "XYZ").forEach(LOGGER::info);

Even Intellij IDE highlights s -> LOGGER.info(s) with yellow and suggests changing it to LOGGER::info .

---

I tried to define a custom class:

static class Consumer
{
    void consume(String s)
    {
        LOGGER.info(s);
    }
}

and use it in place of LOGGER::info :

Consumer consumer = new Consumer();
Arrays.stream(new String[]{"ABC", "DEF", "XYZ"}).forEach(consumer::consume);

It prints into the log!

---

The Logger class has two overloaded methods:

void info(String msg)

and

void info(Supplier<String> msgSupplier)

but only the first is assignable to void forEach(Consumer<? super T> action) , I believe.

Answer 1

Consider that code:

Arrays.stream(new String[]{"ABC"}).forEach(LOGGER::info);
Arrays.stream(new String[]{"ABC"}).forEach(s -> LOGGER.info(s));

The difference is in the first case source of message is:

java.util.Spliterators$ArraySpliterator

in the second:

Main

Probably your logger has some filter that does not let logging events from java.util.Spliterators$ArraySpliterator class.

Try to check result of LOGGER.getFilter()